libaom v3.1.0 Celestia RC1

[Wan-Teh Chang]

Hello everyone,

libaom v3.1.0 release candidate 1 (v3.1.0-rc1) was just tagged[1].

Please test libaom v3.1.0-rc1 and file issues here[2] if you run into
any problems.

Thanks.

[1] https://aomedia.googlesource.com/aom/+/refs/tags/v3.1.0-rc1
[2] https://bugs.chromium.org/p/aomedia/issues/entry

This release adds an "all intra" mode to the encoder, which significantly
speeds up the encoding of AVIF still images at speed 6.

- Upgrading:
All intra mode for encoding AVIF still images and AV1 all intra videos:
AOM_USAGE_ALL_INTRA (2) can be passed as the 'usage' argument to
aom_codec_enc_config_default().

New encoder control IDs added:
- AV1E_SET_ENABLE_DIAGONAL_INTRA: Enable diagonal (D45 to D203) intra
prediction modes (0: false, 1: true (default)). Also available as
"enable-diagonal-intra" for the aom_codec_set_option() function.

New aom_tune_metric enum value: AOM_TUNE_BUTTERAUGLI. The new aomenc option
--tune=butteraugli was added to optimize the encoder’s perceptual quality by
optimizing the Butteraugli metric. Install libjxl (JPEG XL) and then pass
-DCONFIG_TUNE_BUTTERAUGLI=1 to the cmake command to enable it.

Addition of support for libvmaf 2.x.

- Enhancements:
Heap memory consumption for encoding AVIF still images is significantly
reduced.

- Bug fixes:
Issue 2950: Conditional expression for rc->this_key_frame_forced is always
true in find_next_key_frame()

Issue 2988: "make install" installs the aom.h header twice

Issue 2992: Incorrectly printing the temporal_id twice in dump_obu tool